The present invention generally relates to a novel fluid control valve, more particularly an injection valve comprising a plurality of microvalves for injecting discrete charges of gas into a mobile phase or carrier stream, which is particularly useful in high resolution gas chromatography. Further, the present invention provides for parallel arrays of gas injection valves in which multiple samples may be injected into multiple carrier streams substantially simultaneously.
The parallel injection valves of the present invention can be advantageously incorporated into parallel detection systems, including especially parallel gas chromatographs. In a preferred application, the parallel injection valves can be used in conjunction with a multi-channel gas chromatograph as disclosed in U.S. Ser. No. 09/801,430, entitled xe2x80x9cParallel Gas Chromatograph with Microdetector Arrayxe2x80x9d filed Mar. 7, 2001 by Srinivasan et al.
Such parallel detection systems are of substantial importance for high-throughput combinatorial catalysis research programs, wherein chemical reactions are conducted simultaneously using small volumes of reaction materials to efficiently and economically screen large libraries of chemical materials. Preferred parallel screening reactors include the parallel flow reactors as disclosed in U.S. Pat. No. 6,149,882 to Guan et al., U.S. Ser. No. 09/518,794 filed Mar. 3, 2000 by Bergh et al., U.S. Ser. No. 60/185,566 filed Mar. 7, 2000 by Bergh et al., U.S. Ser. No. 60/229,984 filed Sep. 2, 2000 by Bergh et al., U.S. Ser. No. 09/801,390, entitled xe2x80x9cParallel Flow Process Optimization Reactorxe2x80x9d filed Mar. 7, 2001 by Bergh et al., U.S. Ser. No. 09/801,389, entitled xe2x80x9cParallel Flow Reactor Having Variable Feed Compositionxe2x80x9d filed Mar. 7, 2001 by Bergh et al., and U.S. Ser. No. 60/274,065, entitled xe2x80x9cParallel Flow Reactor Having Improved Thermal Controlxe2x80x9d filed on Mar. 7, 2001 by Bergh et al. These reactors can effect reactions in tens, hundreds or even thousands of channels simultaneously or substantially concurrently.
In more advanced online gas monitoring applications such as the high-throughput combinatorial catalysis research programs described above, it is possible to produce sample streams of fluid at various pressures. Most often the samples are at a different pressure than the carrier stream of the gas chromatograph. Injecting samples into a carrier stream at a different pressure is undesirable as pressure gradients can cause sample dispersion, which results in unwanted band broadening that may detrimentally affect the quality of the analysis of the sample. Moreover, pressure difference between samples makes the sample sizes different. Thus, it is important to be able to depressurize the sample after collection, and before injection or transfer to an analysis system, to minimize band broadening and to ensure accurate, reliable analysis.
WO 00/23734 discloses a gas chromatography apparatus comprising a multi-valve assembly including a series of microvalves for sample injection. The multi-valve assembly comprises a series of plates and diaphragms wherein fluid flow is controlled by two pistons. A pressurized actuation gas operates to alternately elevate one or the other of the pistons, which acts to either open or close an individual microvalve. The disclosed multi-valve assembly incorporates six individual microvalves which operate in combination in the same way as a standard 6-port rotary injection valve known in the art of fluid control. Thus, the microvalves of the reference do not provide for sample depressurization prior to sample injection. Further, the rotary arrangement of the disclosed multi-valve assembly limits the size of the valve apparatus such that it is not compatible with or readily capable of being incorporated in a large, parallel chromatography array.
Unlike the prior art, the present invention discloses a gas injection valve comprising a plurality of novel microvalves that can be arranged in valving schemes relevant to online gas analysis applications, for example, allowing a discrete sample of a gas to be depressurized prior to transfer or injection into an analysis apparatus or reaction system.
Among the several objects and features of the present invention may be noted the provision of a gas injection valve comprising one or more microvalves; the provision of such an injection valve wherein each microvalve is capable of being independently actuated; the provision of such an injection valve that may be micro-fabricated; the provision of such an injection valve capable of receiving gas at different pressures and emitting discrete charges of gas at approximately the same pressure; and the provision of such an injection valve which may be incorporated into a parallel array of injection valves for handling multiple gas samples substantially simultaneously.
Briefly, therefore, apparatus of the invention is a microvalve assembly for use in receiving gas at different pressures and emitting discrete charges of gas at approximately the same pressure. The microvalve assembly comprises a valve body having a gas inlet passage adapted for connection to a line for receiving gas at different pressures, a gas outlet passage, a gas charge loop and a pressure control port. The microvalve assembly further comprises (1) a first microvalve associated with the valve body adapted to admit gas passing into the gas inlet passage into the gas charge loop in a first position of the valve and to block entry of gas from the gas inlet passage into the gas charge loop in a second position; (2) a second microvalve associated with the valve body adapted to open the gas charge loop to the pressure control port for reducing the pressure of gas in the gas charge loop in a first position and to block the gas charge loop from the pressure control port in a second position; and, (3) a third microvalve associated with the valve body adapted to open the gas charge loop to the gas outlet passage for emitting the discrete charge of gas from the gas loop from the valve body in a first position and to block the gas charge loop from the gas outlet passage in a second position.
Further, apparatus of the invention include an injection valve array capable of controlling fluid flow from multiple sources substantially simultaneously. The injection valve array comprises multiple injection valves arranged generally adjacent in a linear or curvilinear array. Each injection valve comprises at least one microvalve including (1) a first plate having inlet passages, outlet passages, and fluid transfer channels in a first face, the fluid transfer channels extending between respective pairs of inlet passages and outlet passages to permit fluid communication between the pairs of inlet and outlet passages of said first plate extending between the inlet and outlet passages for fluid communication therebetween; (2) a second plate in generally opposed relation with the first face of the first plate and having piston receptacles toward the first face of the first plate; (3) a sealing membrane located between the first face of the first plate and the second plate; and, (4) a piston for each of said piston receptacles of the second plate, each piston being at least partially disposed in the piston receptacle and movable relative to the first plate between an open position in which the sealing membrane does not block fluid flow in a corresponding one of the fluid transfer channels between the inlet passage and outlet passage, and a closed position in which the piston deforms the sealing membrane to block fluid flow in said corresponding one of the fluid transfer channels between the inlet passage and outlet passage.
Further, apparatus of the invention include a gas injection valve for use in injecting gas samples at controlled pressure into a gas chromatograph. The gas injection valve comprises a gas sample inlet port; a carrier gas inlet port; a gas sample loop; a waste port; a pressure control port; an outlet port; passaging extending between the gas sample inlet port, the carrier gas inlet port, the gas sample loop, the waste port, the pressure control port and the outlet port; and microvalves at least partially disposed in said passaging for selectively blocking the flow of gas between the gas sample inlet port, the carrier gas inlet port, the gas sample loop, the waste port, the pressure control port and the outlet port except through the microvalves. The microvalves are operable to (1) a first state in which the gas sample inlet port is in fluid communication with the sample loop and the waste port, and the carrier gas inlet port is in fluid communication with the outlet port, (2) a second state in which the gas sample loop is blocked from the gas sample inlet port and in fluid communication with the pressure control port for controlling the pressure of the gas in the gas sample loop, the gas sample inlet port is in fluid communication with the waste port, and the carrier gas inlet port remains in fluid communication with the outlet port, and (3) a third state in which the carrier gas inlet port is in fluid communication with the gas sample loop and the gas sample loop is in fluid communication with the outlet port for injecting the gas in the gas sample loop out of the valve through the outlet port.
Still further, apparatus of the invention includes a parallel injection valve for simultaneously injecting each of four or more gas samples into a mobile phase for fluid communication with one of four or more gas chromatography columns of a gas chromatograph. The parallel injection valve comprises four or more microvalve assemblies, each of the four or more microvalve assemblies being adapted to receive one of the four or more samples into a sample loop at a first pressure, to change the pressure of the sample to a second pressure while the sample resides in the sample loop, and to discharge the changed-pressure sample into the mobile phase.
Still further, the invention is directed to a combinatorial chemistry reaction and evaluation system. The system comprises (1) a reactor including multiple reaction chambers adapted for receiving inputs and creating reaction product gas samples at different pressures; (2) an array of injection valves connected to the reactor for receiving the gas samples at different pressures, the injection valves each being adapted to segregate a discrete sample of gas, control the pressure of the sample and emit the discrete gas sample; and, (3) a gas chromatograph having multiple sample columns and a detection system comprising four or more flow detectors, the gas chromatograph being connected to the injection valve array for receiving parallel discrete samples from the injection valve array and analyzing the composition of the samples in parallel.
Still further, the invention is directed to a method of injecting discrete gas samples at a controlled pressure to a gas chromatograph for analysis. The method comprises receiving sample gas to be analyzed into an injection valve; feeding the received sample gas through a sample loop; isolating the sample loop from receiving further sample gas; controlling the pressure of the gas in the sample loop; and injecting the controlled pressure sample gas in the sample loop into the gas chromatograph.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.